This invention relates to an IC card system which is capable of clearly indicating a remaining portion of a history data storage area of a memory in an IC card for transactions, etc, within its incorporated integrated circuit.
The present time has recently been called a "cashless" age, and commodities can be cashlessly purchased with the use of a card issued by a credit card company. etc.
Of the conventional cards available, use is made of plastic cards, embossed cards, magnetic stripe cards, etc. However, these cards may be easily forged, presenting an "unauthorized use" problem.
In order to solve such a problem, an information card or so-called IC card may be conceived which includes an IC circuit with a memory section for storing, for example, a code number. An IC card system based on a combination of an IC card and card terminal has now been developed in this field of art.
In the conventional IC card system, when, for example, a purchase is to be made on credit with the use of an IC card, the IC card is inserted into the card terminal. Then, the code number, for example, is keyed in and confirmed by the system. Then a credit processing is implemented by keying in credit information. At the same time, that information is stored as history data in the history data storage area of a data memory in the IC card.
For the history data memory of the IC card, use is made of an erasable programmable read only memory (EP-ROM) or electrically erasable programmable read only memory (EEP-ROM).
The conventional system, however, has no means for clearly indicating a remaining portion of the history data storage area in the data memory of the IC card. In the EP-ROM type in particular, however, there is a possibility that the IC card will suddenly be found unsuitable at some time due to the data storage area being completely filled. In the EEP-ROM type, on the other hand, when the data storage area of the data memory is filled, the oldest data stored is deleted by the socalled "overlay" and thus replaced with new data.
In the former case, the user will be unduly inconvenienced when he finds the IC card unsable after a purchase of commodities at a store. In the latter case, the history data may be unintentionally erased forever, with the result that it cannot be read out later.